Marker Tool
==============

Add a marker tool to edit or add infotext to nodes.

There are 3 settings are applied in this order :

 * Setting `marker_tool_allowed_nodes` is a whitelist : If it is not set, all nodes are considered allowed. Otherwise, all nodes NOT listed won't be editable by players without infotext_editor priv
 * Setting `marker_tool_ignored_nodes` is a blacklist : Any node listed in the setting, won't be editable by players without infotext_editor priv. Even if they are whitelisted.
 * Setting `marker_tool_restrict_create` will prevent players without infotext_editor priv to create new infotexts, they will only be able to edit node with an existing infotext (among those allowed and not ignored)

Players with infotext_editor can edit anything if they are admin
Other players can never edit anything belonging to someone else
